The detection of tricycloalkanes appears to be more definite with FI than with EB, since no data were reported in the latter case. The same is true of the indans and tetralins, whose presence in the sample was reported by some of the laboratories using EB mass spectrometers and not by others. The molecular weight distribution for the groups is given directly by the FI mass spectra. To summarize, therefore, the analysis of high-boiling hydrocarbon mixtures containing many components by means of an FI mass spectrometer is much simpler if the sensitivity coefficients of the groups of substances are constant. Long calculations are avoided in the evaluation of the spectra, and it is unnecessary to solve extremely large matrix systems or to make allowance for the masking of fragments of heavier components by the lighter components. The detection of trace components in a mixture is more definite with FI than with EB; this observation is not confined to the highboiling hydrocarbon mixtures discussed here.Finally, it should be mentioned that Wanless 163,641 has constructed "FI metastable maps", which simplify[63] G. G. Wanless and G. A . Glock jr., Analytic. Chem. 39, 2 (1967).
Nucleophilic acylation is the attachment of an R-C=O group to an electrophilic center. A brief discussion of the advantages offered by acylations of this type in syntheses is followed by a description of the direct methods (reactions with acylmetal compounds) and the methods proceeding via "masked" acyl anions. The latter methods are based on the use of either metalated vinyl ether derivatives or carbanions derived from acetals.
Organyllithiums of sulfur-stabilized carbanions are important reagents of this type.The synthetic methods of organic chemistry have always been greatly enriched by the direct or indirect "reversal" of the mode of reaction of a reagent. Thus when water is added to unsymmetrically substituted double bonds, the OH group in the product is always attached to the carbon atom carrying the greater number of alkyl substituents (Murkownikof's rule). 111 A separate review of the dithiane method of nucleophilic acylation has already been published [84].tion would require HO @ as an electrophile, the intermediate resulting from the primary attack by this species then being "neutralized" by an He. This is not C H, c H3 7 H3 I H Scheme 1. R,B-CH2-C-CH, Angew. Chem. internat. Edit. f Vol. 8 (1969) J No. 9 [5] J . and other literature cited therein; b) E. J. Corey and L. S. Hegedus, J. Amer. chem. SOC., in press; c) 91, 1233 (1969). 181 a) Cf. Reaction of phenyllithium with hexacarbonyltungsen to give lithium benzoylpentacarbonyltungstate(O), E. 0. Fischer and A . MaasboI, Angew. Chem. 76, 645 (1964); Angew. Chem. internat. Edit. 3, 580 (1964); Chem. Ber. 100, 2445 (1967); b) M . Schlosser, Angew. Chem. 76, 124 (1964); Angew. Chem. internat. Edit. 3,287 (1964) and literature cited therein; c) cf. also, Hg-derivatives: D. Seyferth and R. J . Spohn, J. Amer. chem. SOC. 91, 3037 (1969).